Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$199.80	5.553%	$210.8949	$210.89	$210.90	$210.90
Purchase #2	$72.89	9.673%	$79.9406	$79.94	$79.95	$79.90
Purchase #3	$197.29	5.736%	$208.6066	$208.61	$208.60	$208.60
Purchase #4	$116.52	12.335%	$130.8927	$130.89	$130.90	$130.90
Purchase #5	$207.99	6.546%	$221.605	$221.61	$221.60	$221.60
Purchase #6	$80.92	6.376%	$86.0795	$86.08	$86.10	$86.10
Purchase #7	$217.55	11.164%	$241.8373	$241.84	$241.85	$241.80
7 purchase totals =	$1,092.96		$1,179.8566	$1,179.86	$1,179.90	$1,179.80